1. Field
This various circuit embodiments described herein relate in general to power converters, and, more specifically, to double phase-shifting full-bridge DC-to-DC power converters having capabilities and advantages of the type described which can be controlled with phase-shifting signals, with a wide-range of zero-voltage-switching (ZVS), and with substantially no circulating currents.
2. Background
In the field of power conversion, it is a common practice to convert electrical energy from one DC voltage level to other isolated DC voltage levels using high frequency switching technology. The use of switching technology dramatically decreases the size of power converters and improves power conversion efficiency. While enjoying the benefits of switching technology, industry is also facing new challenges, including further demands of higher power conversion efficiency, smaller converter size requirements, and lower electromagnetic inference (EMI) emission requirements that are caused by switched currents and voltages.
In order to improve converter efficiency, reduce the size of converters, and minimize EMI, tremendous efforts have been made to achieve wide-range zero voltage switching (ZVS), eliminate circulating currents, perform energy recovery associated with reverse recovery of output diode, and eliminate or clamp voltage ringing of the output diodes. Although a lot of effort has been expended, no comprehensive solution known to the applicant has been achieved that has a wide-range ZVS capability, always operates at maximum duty cycle, fully utilizes magnetic components, minimizes or eliminates circulating current, performs reverse energy recovery, and clamps or eliminates the voltage ringing at output diodes.
What is needed is a DC-to-DC converter and control method with topology that can operate at a constant 50% duty cycle with a regulated output voltage. Also, what is needed is a control method and topology that can improve peak efficiency and light load efficiency at the same time, without having to switch between PWM and phase-shift control signal modes.